Circular fluorescent lamp with two-piece snap-lock base

ABSTRACT

A plastic base assembly for a &#39;&#39;&#39;&#39;circline&#39;&#39;&#39;&#39; fluorescent lamp is molded in two segments that are secured in enclosing relationship with the sealed ends of the envelope solely by means of a snapinterlock effected between a pair of depending lugs on one of the segments and a pair of mating recesses in the other segment. The base segment having the locking lugs is molded in such a way that the side walls of the lugs define a locking angle that is smaller than the mold release angle and thus permits the base segment to be readily stripped from the molding die without damaging or otherwise impairing the ability of the lugs to effect a strong mechanical interlock with the other base segment. Rotation of the base relative to the lamp envelope is prevented by a nodal projection on the enclosed end of the envelope that is located between stop means molded into the inner surface of one of the base segments. Alternatively, the ends of the lamp envelope can be provided with metal end caps one of which has a tang that is disposed between the stop means defined by the base structure.

United States Patent [1 1 Livera Aug. 5, 1975 [75] Inventor: Phillip A. Livera, Bloomfield, NJ.

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

[22] Filed: Apr. 5, 1974 [21] Appl. No.: 458,380

[52] US. Cl 313/51; 24/257 R; 264/334; 313/318; 339/50 C; 403/344 [51] Int. Cl. HOlJ 5/60; B28B 13/05 [58] Field of Search 313/51, 318; 339/50C; 403/344, 375; 46/25; 24/201 C, 257, 284, 285, 201 S [56] References Cited UNITED STATES PATENTS 1,476,509 12/1923 Hart 24/201 C 2,392,785 1/1946 Thomas 313/318 2,453,986 11/1948 Greiner et a1. 313/318 2,626,977 l/l953 l-linman 313/318 3,058,187 10/1962 Gugen 24/201 C 3,546,523 12/1970 Gilbert, .lr 313/318 LUGS OUTER SIDE WALL SURFACE 0F LUG Primary Examiner-Alfred E. Smith Assistant ExaminerWm. l-l. Punter Attorney, Agent, or F irm-D. S. Buleza 5 7 ABSTRACT A plastic base assembly for a circline fluorescent lamp is molded in two segments that are secured in enclosing relationship with the sealed ends of the envelope solely by means of a snap-interlock effected between a pair of depending lugs on one of the segments and a pair of mating recesses in the other segment. The base segment having the locking lugs is molded in such a way that the side walls of the lugs define a locking angle that is smaller than the mold release angle and thus permits the base segment to be readily stripped from the molding die without damaging or otherwise impairing the ability of the lugs to effect a strong mechanical interlock with the other base segment. Rotation of the base relative to the lamp envelope is prevented by a nodal projection on the enclosed end of the envelope that is located between stop means molded into the inner surface of one of the base segments. Alternatively, the ends of the lamp envelope can be provided with metal end caps one of which has a tang that is disposed between the stop means defined by the base structure.

14 Claims, 8 Drawing Figures OUTER SlDE WALL SURFACE OF LUG PATENTEU AUG 5 INNER SIDE WA SURFACES OF FIG. 4

PATENTED AUB 51975 (fl-TL" unLLl OUTER SIDE WALL SURFACE OF LUG SURFACES OF LUGS CIRCULAR FLUORESCENT LAMP WITH TWO-PIECE SNAP-LOCK BASE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention generally relates to electric lamps and has particular reference to a circular fluorescent lamp having an improved snap-lock base and to a method of manufacturing such bases.

2. Description of the Prior Art Base assemblies for circular-shaped fluorescent lamps that are snap-locked onto the ends of the lamp envelope and connect the lead wires of the lamp to terminal means carried by the base assembly are generally well-known in the art. A base of this type that is attached to the ends of the lamp envelope by a split sheet-metal sleeve which is locked in place by an indent and tab arrangement provided on overlapping edge portions of the sleeve is disclosed in US. Pat. No. 2,733,417 issued Jan. 31, 1956 to Hinman et al. A socket assembly of plastic material that is designed to be snap-fitted around the ends of straight tubular fluoresccnt lamps that are arranged in either end-to-end relationship or at right angles to one another is disclosed in US. Pat. No. 2,814,787 issued Nov. 26, 1957 to J. D. .lessup.

A more recent base assembly for a circular fluorescent lamp wherein a pair of base segments that are molded from plastic are fastened to the ends of the lamp envelope by interlocking tongues and lips provided on the base segments is disclosed in US. Pat. No. 3,546,523 issued Dec. 8, 1970 to M. N. Gilbert, Jr. Another type of snap-lock base for a circular fluorescent lamp is described in Japanese Utility Model 46-15-989.

A circular fluorescent lamp having an envelope with indented end portions that are fitted with a one-piece base is disclosed in US. Pat. No. 3,274,420 issued Sept. 20, 1966 to Kameyama et al.

While the prior art base assemblies were satisfactory from the standpoint of providing a protective enclosure for the bulb ends and lead wires and connecting the lamp to an electrical socket, they were rather expensive to manufacture and assemble and did not have a reliable interlock. Molding the base parts from plastic material presented a particularly difficult manufacturing problem in that the base segment having the protruding locking elements stuck in the molding die and sometimes could not be stripped from the die without damaging the locking elements. This, in turn, weakened the interlocking juncture of the base segments and presented a serious quality control problem insofar as the base segments could work loose and separate during use or shipment of the finished lamps.

SUMMARY OF THE INVENTION The foregoing quality control and manufacturing problems are solved in accordance with the present invention by making the two segments of the base assembly of such configuration that they can be readily molded from plastic and quickly stripped from the molding dies without damaging the parts or impairing their ability to be securely fastened together in assembled relationship with the lamp envelope solely by means of a snap-interlocking fit.

Briefly, the foregoing advantages are obtained by employing locking lugs on one of the base segments that are so shaped that they provide a mold release angle that is greater than the locking angle of the lugs. Correlating the angular orientation of the lug surfaces in this manner provides a tapered contour which permits the lugs to clear the molding die when the base segment is being stripped from the molding die. The lugs can thus effect the deep interlock with the other base segment necessary to lock the segments together around the lamp ends in a secure and positive manner.

The snap-interlocking action can be further enhanced, in accordance with one embodiment, by providing thin ridges on the outer faces of the locking lugs that nestingly engage and fit into undercut grooves in the other base segment when the base is snap-fitted onto the ends of the lamp envelope.

Each of the base segments are also contoured to provide thick-walled central portions and thin-walled skirt portions that permit the lamp to be inserted into its socket without cracking the plastic and protectively enclose the sealed ends of the bulb, respectively. A very simple and practical arrangement for limiting the rotational movement of the assembled base relative to the lamp envelope is also provided wherein portions of one or both of the base segments define interior stop means that cooperate with glass nodules molded in the associated sealed end of the lamp envelope, or with a tang on a metal cap that is secured to one of the envelope ends. This prevents excessive movement of the base accidental damage to or breakage of the attached lead wires.

BRIEF DESCRIPTION OF THE DRAWINGS.

A better understanding of the invention will be obtained from the exemplary embodiments shown in the accompanying drawing, wherein:

FIG. 1 is a side elevational view of a portion of a circular fluorescent lamp that is fitted with the improved snap-lock base assembly of the present invention, portions of the base and lamp envelope being removed for illustrative purposes;

FIG. 2 is an enlarged cross-sectional view through the central portion of the base assembly along line 11-11 of FIG. 1, in the direction of the arrows;

FIG. 3 is a similar view, along line IIIIII of FIG. 1, showing the stud-nodule arrangement for limiting the rotational movement of the base relative to the envelope;

FIG. 4 is an exploded perspective view of the molded plastic base segments shown in the preceding figures, prior to the insertion and staking of the terminal pins;

FIG. 5 is an enlarged sectional view of the based portion of a circular fluorescent lamp illustrating an alternative embodiment of the invention;

FIG. 6 is an exploded perspective view of the two base segments employed in the lamp shown in FIG. 5;

FIG. 7 is a cross-sectional view through the central portion of the base assembly shown in FIG. 5 illustrating the relationship of the locking angle and mold release angle provided by tapering the locking lugs in accordance with the invention; and,

FIG. 8 is a cross-sectional view of a molding die and a newly-formed plastic base segment illustrating the manner in which the base segment is quickly stripped from the die without damaging the locking lugs.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. I, the improved base construction of the present invention is particularly adapted for use in conjunction with a circular fluorescent lamp L having a vitreous envelope that is bent into annular configuration so that its sealed ends are spaced from one another and disposed in opposing relationship. The envelope 10 has an inner coating 11 of a suitable phosphor and is dosed with mercury and a fill gas through an exhaust tube 12 which is then tipped-off in accordance with standard lamp-making practice. Each end of thecnvelope 10 is sealed to a glass stem 13 that is fused to the open end of the exhaust tube 12 in the usual manner. A pair of lead wires 14 and 15 are hermetically sealed through the stem 13 and are fastened to an electrode 16 consisting of the usual tungsten wire coil that is coated with suitable electron-emission material.

The opening or gap between the sealed ends of the envelope 10 is spanned by the improved base assembly B of the present invention, which assembly consists of two base segments 20 and 21 that are snap-locked together in enclosing relationship with the ends of the envelope. The lead wires 14 and 15 extend into the base B and into selected ones ofa set of four hollow terminal pins 22 that are anchored in base segment 21. The lead wires are connected to the pins in a suitable manner, such as by welding them to the outer ends of the pins.

As will be noted in FIGS. 1 and 3, the ends of the lamp envelope 10 that are enclosed by the base assembly B are each provided with a circumferential indentation 17 and two pairs of short studlike projections 23-24 and -26 on the inner wall surfaces of at least one end of the respective base segments 20 and 21 extend into the associated indentation. As shown in FIG. 3, the indented end portions 17 of the envelope 10 are each provided with two protrusions such as nodules 18 that are molded into and comprise parts of the bulb wall and are located 180 from each other. These nodules 18 bridge the bulb indents 17 and are located between the two sets of stud-like projections 23-24 and 25-26 on the enclosing parts of the respective base segments 21 and 20. Rotational movement of the base B relative to the lamp envelope 10 is thus limited to the distance between projections 23 and 24 (and projections 25 and 26) which thus serve as integral stop means.

The configuration of the base segments 20 and 21 is clearly shown in FIG. 4. As illustrated, base segment 21 is of generally semi-cylindrical configuration and has a thick-walled central portion that consists of an inwardly-protruding boss 27 that merges with an arcuate ledge 28. A pair of locking lugs 29 and 31 protrude from the inner surface of this ledge and beyond the planar faces 34 and 35 of the base segment 21 that constitute its side edges. A ridge 32 extends along the outermost edge of lug 31 and a ridge 30 extends along the center and the outer face of the lug 29. The terminal pins 22 are anchored in four holes 33 in the boss 27 and extend beyond a flat outer wall 36 provided on this port of the base segment (see FIG. 2). The arcuate end sections of the base segment 21 disposed on either side of the i thick-walled central portion have relatively thin walls and comprise skirts 37, 38 which enclose the sealed ends of the envelope 10 when the base segments are locked in assembled relationship. Skirt 37 has the aforementioned stud-like projections 25, 26.

The other base segment 20 is also of semi-cylindrical configuration and has a thick-walled central portion consisting of two arcuate reinforcing ribs 39 that are LII (all

joined by longitudinal ledges 40 and 41 which merge with the side edges of the segment 20 and define therewith the planar faces 42 and 43 of this segment. Ledge 40 has a slot-like recess 44 and undercut groove 45 that snugly accommodate and effect a snap-interlock with the ridged lug 31. Ledge 41 also has a slot-like recess 46 and undercut groove 47 which mate and snapinterlock with the other ridged lug 29. Recesses 44 and 46 are located inwardly from the respective planar faces 42 and 43 of the base segment 20. The end sections of base segment 20 are also thin-walled and constitute a pair of skirts 48 and 49. Skirt 49 has the projecting studs 23 and 24 on its inner surface.

Base segments 20 and 21 are securely fastened to one another in snap-interlocking relationship in the manner shown in FIG. 2. As will be noted, locking lugs 29 and 31 of base segment 21 nestingly engage and mate with the recesses 44 and 46 in segment 20 so' that the planar faces of the two base segments are seated in tight abutting relationship. The outwardly-facing side walls of the locking lugs 29 and 31 that are contiguous with the planar faces 34, 35 of base segment 21 are coincident with planes that define a locking angle that is smaller than the angle formed by the planes that are coincident with the side walls of the lugs that face inwardly and toward one another, which angle constitutes the mold release angle as hereinafter described. The locking lugs 29 and 31 are thus tapered in a manner such that they become thinner in cross-sectio nas one proceeds from their root ends toward their free ends.

As will also be noted in FIG. 2, the outer wall 36 of the base segment 21 opposite the boss 27 is flat and defines a recess that extends transversely across the arcuate contour of the base assembly B and accommodates the exposed portions ofthe terminal pins 22 so that the latter are almost entirely recessed within the confines of the base B.

ALTERNATIVE EMBODIMENT (FIGS. 5-7) An alternative embodiment of the invention is shown in FIGS. 5-7. According to this embodiment. the circular fluorescent lamp Lu has an envelope 10a with sealed ends that are provided with metal end caps50 and 51 that are sealed to the annular rims of the envelope and provide means for gripping the envelope when it is bent into its circular shape. In contrast to the previous embodiment. rotational movement of the base Ba relative to the lamp envelope 10a is restricted by a protruding tang 52 on the metal end cap 51, which tang is disposed between a pair of shoulders 53 provided on the inner s i rface of base segment 200. As shown more clearly in FlG 6, these shoulders 53 constitute upstanding integral parts of an arcuate ledge 390 that is molded into the inner surface of the base segment 20a and define its thick-walled central portion.

In contrast to the previous embodiment. the recesses 44a and 46a (see FIG. 6) in base segment 20a do not have undercut grooves and are configured to snapinterlock with smooth tapered lugs 29a and 310 that extend outwardly from the planar faces 34a and 35a of the other base segment 21a The inwardly-protruding boss 27a and arcuate ledge 28a provide base segment 21a with a thick-walled central portion and thin-walled skirts 37a. 3811 as in--the previous embodiment. Base segment 20a also has thin-walled skirt sections 48a. 49a.

As shown in FIG. 5, the lead wires 14a and Isaextend from the respective glass stems 1311 into selected ones of the hollow terminal pins 22a to which they are electrically connected. The envelope a is provided with the usual interior coating 11a of suitable phosphor and the inner ends of the lead wires are attached to suitable electrodes 16a. When the base segments 20a and 21a are snap-locked onto the sealed ends of the envelope 10a, their planar faces 34a-35a and 42a-43a are clamped in abutting relationship and the skirt sections 37a, 38a, 48a and 49a protectively enclose the sealed ends of the envelope 10a and the metal end caps 50 and 51 (see FIG. 5).

The relationship between the locking angle and mold release angle provided by the locking lugs 29a, 31a and the manner in which the lugs securely fasten the base segments 20a and 2111 together solely by means of a snap-lock fit'is shown in FIG. 7. As will be noted, the outwardly-disposed side wall surfaces of the locking lugs 29a and 31a lie in planes that define a locking angle a that is smaller than the mold release angle B that is defined by the planes that are coincident with the inwardly-facing side wall surfaces of the locking lugs. The locking lugs 29a and 31a are thus tapered in cross-section and provide the clearance necessary to permit base segment 21a to be readily stripped from the molding die during manufacture Angle B should exceed angle a by at least 10. As a specific example, satisfactory stripping of the male base segment 21a from the molding die and a secure interlock between the assembled base segments have been achieved with a locki'ngangle of approximately 20 and a mold release angle of approximately 36. A locking angle of from about 16 to 24 and a mold release angle of from about 32 to 40 can be employed provided they are properly correlated.

As shown in FIG. 8, the male base segment 21a is stripped from its molding die 54 by a stripping pin 58 that extends through the die and is movable toward the inner surface of the base segment 210 along a path that intersects the plane which joins the locking lugs 29a and 310. Of course, the molding die 54 has slot-like recesses 55 and 56 which are contoured to provide locking lugsofthedesired shape and the die has other portions that are contoured to provide the desired interior configuration of the base 21a, as will be understood to those skilled in the .art. It will also be appreciated that molding die 54 cooperates with another die (not shown) that seats against the flat undersurfaces 60, 61 of die 54 andforms a two-piece mold assembly that defines a mold cavity which is contoured to give the base segment 21a its smooth outer configuration.

After the-plastic resin is injected into the mold cavity and the formedbase segment 21a has been cured and rigidified, the mold assembly is opened and stripping pin 58 is moved downwardly, as viewed in FIG. 8 thereby applying a force tothe newly-formed base segment 210 that temporarily flexs and compresses ltuThiS displaces the locking lugs 29a and 31a toward each a distance such that they clear the recessed edges of the die 54 thus permitting base segment 21a to drop out of the die 54.

The base segments 20, 20a, and 21, 21a are molded from a suitable thermo plastic material, such as polystyrene. that is hard and durable yet resilient enough to permit the base segments to be temporarily deformed during the stripping action (and snap-interlocking operation) and then spring back to their original positions. The plastic is desirably impregnated with a white pigment so that the finished bases B and Ba closely match the white color of the phosphor-coated envelopes and give the completed lamp assemblies a very pleasing appearance.

A suitable thermo setting plastic such as whitepigmented formaldehyde resin can also be used to make segments 20a and 21a.

While the locking angle a and mold release angle B I have been depicted in FIG. 7 in connection with the alternative base embodiment Ba, the same angular correlation is employed in the lamp and base embodiments shown in FIGS. 1-4. The supplementary locking ridges 30 and 32 employed on the locking lugs 29 and 31 of base segment 21 are so short and thin that they do not materially alter or interfere with the stripping operation even though the recessed portions of the molding die in this embodiment are suitably undercut with grooves that form the ridges. The resiliency of the cured plastic material is such that base segments of this type can readily be stripped from the molding die simply by increasing the force applied to the molded base segment by the stripping pin. While the ridges 30 and 32 are temporarily deformed and flexed transversely during the stripping action, they .immediately return to their original positions as soon as the base segment 21 is separated from the die.

I claim as my invention:

1. A low-pressure gaseous discharge lamp comprising, in combination; H

a tubular vitreous envelope of annular configuration having sealed ends that are disposed in spaced opposing relationship,

a hollow base of resilient electrically non-conductive material consisting of two segments that are disposed in enclosing relationship with the sealed ends of said envelope and span the opening therebetween, each of said base segments having planar faces that constitute the side edges of the base segments and are held in abutting relationship along a plane that extends across the opening between and intersects the sealed ends of the envelope,

terminal means secured to one of said base segments,

flexible lead wires extending from the sealed ends of said envelope into said base and connected to said terminal means, and

means holding the base segments in the aforesaid enclosing and spanning relationship with the sealed ends of said envelope and in abutting relationship with each other solely by means of a frictional interfitting of said base segments,

said holding means comprising a pair of slot-like recesses in a central portion of one of said base segments and located inwardly from the planar faces thereof, and a pair of elongated integral locking lugs on the central portion of the other of said base segments that are located inwardly from and extend beyond the respective planar faces thereof and are seated in mating and snap-interlocking relationship with the slot-like recesses in said one base segment,

the inwardly-disposed and outwardly-disposed side wall surfaces of said pair of lugs being substantially flat along the region that is contiguous with the planar faces of the associated base segment and lying in planes that are tilted relative to one another in a manner such that the angle defined by the planes which are coincident with the inwardly-disposed side wall surfaces of said lugs is greater than the angle which is defined by the planes that are coincident with the outwardly-disposed side wall surfaces of said lugs.

2. The discharge lamp of claim 1 wherein;

said base segments are of generally semi-cylindrical configuration, and

one of the sealed ends of the envelope has a protruding component that extends into a region inside the base that is delineated by stop means which constitutes part of the base structure and cooperates with said protruding component to limit the rotational movement of said base relative to the envelope.

3. The discharge lamp of claim 2 wherein;

said envelope is of substantially circular configuration, contains mercury and has a layer of phosphor on its inner surface and said lamp thus comprises a fluorescent lamp, and

said base segments are composed of plastic.

4. The fluorescent lamp of claim 3 wherein;

said protruding component comprises a nodular protrusion that extends laterally from the surface of one of the sealed ends of said vitreous envelope, and

said stop means comprises a pair of spaced stud-like projections on the inner surface of one of said base segments that are located on opposite sides of the nodular protrusion on said one end of the envelope.

5. The fluorescentlamp of claim 4 wherein;

the portion of the sealed end of said envelope having said nodular protrusion is circumferentially indented, and

said stud-like projections are disposed on the arcuate end section of said one base segment that overlies the indented portion of said envelope end.

6. The fluorescent lamp of claim 3 wherein;

said protruding component comprises a depending tang on a metal cap that is fastened to the sealed end of the envelope, and

said stop means comprises a pair of spaced shoulders in the central portion of one of said base segments that are located on opposite sides of said tang.

7. The fluorescent lamp of claim 3 wherein;

said terminal means comprises hollow metal pins that are anchored in holes that extend through the central part of one of said base segment, and

said lead wires extend into selected ones of said metal pins and are connected thereto.

8. The fluorescent lamp of claim 7 wherein;

the central part of said one base segment in which the metal pins are anchored comprises an inwardlyprotruding boss, and

the exterior surface of said one base segment opposite said boss is substantially flat and defines a cavity that extends transversely across the arcuate contour of said base and aeccommodates the outer ends of said metal pins and thereby at least partly recesses the pins wihtin the confines of the base.

9. The fluorescent lamp of claim 3 wherein; each of the locking lugs on said base segment has a ridge that extends longitudinally along the outer side wall of the respective lugs, and each of the recessed portions of the other base segment has an undercut groove that accommodates one of said ridges.

10. The fluorescent lamp of claim 3 wherein the angle defined by the planes that are coincident with the inwardly-disposed side wall surfaces of said locking lugs is at least l0 greater than the angle defined by the planes which are coincident with the outwardlydisposed side wall surfaces of said lugs.

11. The fluorescent lamp of claim 10 wherein;

the angle defined by the planes that are coincident with the inwardly-disposed side wall surfaces of said locking lugs is approximately 36, and

the angle defined by the planes which are coincident with the outwardly-disposed side wall surfaces of said lugs is approximately 20. 7 12. In the manufacture of a two-piece snapinterlocking base assembly for a fluorescent lamp or similar device wherein the base segments are molded from a resilient plastic and one of the base segments has a pair of locking lugs the protrude from the sides of said segment and are conformed to effect a resilient snap-interfitting juncture with mating recesses .in the other base segment, the method of manufacturing the base segment having said locking lugs comprising;

providing a mold assembly that defines a mold cavity of the same configuration as said base segment and thus includes a die that has a pair of spaced recesses of the same configuration as the locking lugs.

shaping the die so that the side walls thereof which, correspond to the outwardly-disposed side walls of the locking lugs lie in planes that define a locking angle which is smaller than the mold release angle that is defined by the planes that are coincident with side walls of the die recesses which correspond to the inwardly-disposed side walls of the locking lugs.

filling the cavity of the mold assembly with uncured plastic resin to form the base segment, and

after the plastic resin has hardened, stripping the formed base segment from the molding die by applying a force to the base segment that is sufficient to temporarily flex the locking lugs inwardly until they clear the recessed portions of the die and the base segment is thus separated from said die.

13. The method of claim 12 wherein said mold release angle is in the range of from about 32 to 40 and said locking angle is in the range of from about l6 to 24.

14. The method of claim 12 wherein the formed plastic base segment is removed from the molding die by a stripping pin that extends through the part of the die which forms the interior portion of the base segment and is movable along a path that intersects the plane which joins the locking lug portions of the formed base segment. 

1. A low-pressure gaseous discharge lamp comprising, in combination; a tubular vitreous envelope of annular configuration having sealed ends that are disposed in spaced opposing relationship, a hollow base of resilient electrically non-conductive material consisting of two segments that are disposed in enclosing relationship with the sealed ends of said envelope and span the opening therebetween, each of said base segments having planar faces that constitute the side edges of the base segments and are held in abutting relationship along a plane that extends across the opening between and intersects the sealed ends of the envelope, terminal means secured to one of said base segments, flexible lead wires extending from the sealed ends of said envelope into said base and connected to said terminal means, and means holding the base segments in the aforesaid enclosing and spanning relationship with the sealed ends of said envelope and in abutting relationship with each other solely by means of a frictional interfitting of said base segments, said holding means comprising a pair of slot-like recesses in a central portion of one of said base segments and located inwardly from the planar faces thereof, and a pair of elongated integral locking lugs on the central portion of the other of said base segments that are located inwardly from and extend beyond the respective planar faces thereof and are seated in mating and snap-interlocking relationship with the slot-like recesses in said one base segment, the inwardly-disposed and outwardly-disposed side wall surfaces of said pair of lugs being substantially flat along the region that is contiguous with the planar faces of the associated base segment and lying in planes that are tilted relative to one another in a manner such that the angle defined by the planes which are coincident with the inwardly-disposed side wall surfaces of said lugs is greater than the angle which is defined by the planes that are coincident with the outwardlydisposed side wall surfaces of said lugs.
 2. The discharge lamp of claim 1 wherein; said base segments are of generally semi-cylindrical configuration, and one of the sealed ends of the envelope has a protruding component that extends into a region inside the base that is delineated by stop means which constitutes part of the base structure and cooperates with said protruding component to limit the rotational movement of said base relative to the envelope.
 3. The discharge lamp of claim 2 wherein; said envelope is of substantially circular configuration, contains mercury and has a layer of phosphor on its inner surface and said lamp thus comprises a fluorescent lamp, and said base segments are composed of plastic.
 4. The fluorescent lamp of claim 3 wherein; said protruding component comprises a nodular protrusion that extends laterally from the surface of one of the sealed ends of said vitreous envelope, and said stop means comprises a pair of spaced stud-like projections on the inner surface of one of said base segments that are located on opposite sides of the nodular protrusion on said one end of the envelope.
 5. The fluorescent lamp of claim 4 wherein; the portion of the sealed end of said envelope havIng said nodular protrusion is circumferentially indented, and said stud-like projections are disposed on the arcuate end section of said one base segment that overlies the indented portion of said envelope end.
 6. The fluorescent lamp of claim 3 wherein; said protruding component comprises a depending tang on a metal cap that is fastened to the sealed end of the envelope, and said stop means comprises a pair of spaced shoulders in the central portion of one of said base segments that are located on opposite sides of said tang.
 7. The fluorescent lamp of claim 3 wherein; said terminal means comprises hollow metal pins that are anchored in holes that extend through the central part of one of said base segment, and said lead wires extend into selected ones of said metal pins and are connected thereto.
 8. The fluorescent lamp of claim 7 wherein; the central part of said one base segment in which the metal pins are anchored comprises an inwardly-protruding boss, and the exterior surface of said one base segment opposite said boss is substantially flat and defines a cavity that extends transversely across the arcuate contour of said base and acccommodates the outer ends of said metal pins and thereby at least partly recesses the pins wihtin the confines of the base.
 9. The fluorescent lamp of claim 3 wherein; each of the locking lugs on said base segment has a ridge that extends longitudinally along the outer side wall of the respective lugs, and each of the recessed portions of the other base segment has an undercut groove that accommodates one of said ridges.
 10. The fluorescent lamp of claim 3 wherein the angle defined by the planes that are coincident with the inwardly-disposed side wall surfaces of said locking lugs is at least 10* greater than the angle defined by the planes which are coincident with the outwardly-disposed side wall surfaces of said lugs.
 11. The fluorescent lamp of claim 10 wherein; the angle defined by the planes that are coincident with the inwardly-disposed side wall surfaces of said locking lugs is approximately 36*, and the angle defined by the planes which are coincident with the outwardly-disposed side wall surfaces of said lugs is approximately 20*.
 12. In the manufacture of a two-piece snap-interlocking base assembly for a fluorescent lamp or similar device wherein the base segments are molded from a resilient plastic and one of the base segments has a pair of locking lugs the protrude from the sides of said segment and are conformed to effect a resilient snap-interfitting juncture with mating recesses in the other base segment, the method of manufacturing the base segment having said locking lugs comprising; providing a mold assembly that defines a mold cavity of the same configuration as said base segment and thus includes a die that has a pair of spaced recesses of the same configuration as the locking lugs, shaping the die so that the side walls thereof which correspond to the outwardly-disposed side walls of the locking lugs lie in planes that define a locking angle which is smaller than the mold release angle that is defined by the planes that are coincident with side walls of the die recesses which correspond to the inwardly-disposed side walls of the locking lugs, filling the cavity of the mold assembly with uncured plastic resin to form the base segment, and after the plastic resin has hardened, stripping the formed base segment from the molding die by applying a force to the base segment that is sufficient to temporarily flex the locking lugs inwardly until they clear the recessed portions of the die and the base segment is thus separated from said die.
 13. The method of claim 12 wherein said mold release angle is in the range of from about 32* to 40* and said locking angle is in the range of from about 16* to 24*.
 14. The method of claim 12 wherein the formed plastic base Segment is removed from the molding die by a stripping pin that extends through the part of the die which forms the interior portion of the base segment and is movable along a path that intersects the plane which joins the locking lug portions of the formed base segment. 